Galvani potential difference

https://doi.org/10.1351/goldbook.G02574
An electric potential difference between points in the bulk of two phases. It is measurable only when the two phases have identical composition (e.g. two copper wires). It is the difference of inner electric potentials in two phases. Symbol: Δαβϕ.
Source:
Green Book, 2nd ed., p. 59 (https://dev.goldbook.iupac.org/files/pdf/green_book_2ed.pdf)